Display technology is an integral part of the productivity of information processing equipment. The use of displays to effectively communicate to the operators of the equipment and others affected by the information being processed has been of fundamental concern to users of the information processing equipment for many years. A particular concern is the difficulty of displaying two sets of information to two different users of the equipment at the same time. This concern arises out of relationships similar to that of a customer and salesperson or a teacher and student. The information processing equipment contains data of interest to both parties, but can only display the data in a single format because of the physical limitations of the display. The data would be more useful to both parties if it was displayed with a different form or emphasis to each party.
The prior art has responded to this problem by developing systems having two different displays, one for each party. In such a system, each display provides the information required by a single party. Providing two displays is an expensive solution and one that few users find acceptable. Another prior art solution to the problem has been to provide windows on a single display. This display reserves different parts of a single screen for different information. This is an improvement, however it still requires both parties to view the same screen, and therefore, it is still inadequate for many purposes. The single screen display limitation is primarily a result of the display having an excitation source which has not been adapted to multiple screen applications. For example, CRTs have electron beams as the excitation source to a phosphoring screen. However, typical generation of the electron beam requires that the phosphoring screen only be viewed from the front of the screen. Similarly, liquid crystal displays (LCDs) depend on light passing through the back of the screen, through the transparent electrodes, and finally through the front of the screen. Viewing the screen from both sides is impossible because either a reflective backing or a light source is on the rear of the screen. In both cases, the excitation source itself inhibits utilizing both sides of the display screen for multiple function purposes.